Synopsis

Input Parameters

Output Parameters

arnorm

- good estimate of norm((A*inv(Pmat))'*r), where r = A*x - b, used in specific stopping criterion

anorm

- poor estimate of norm(A*inv(Pmat),'fro') used in specific stopping criterion

Notes

Output parameters are meaningful only after KSPSolve().
These are the same quantities as normar and norma in MATLAB's lsqr(), whose output lsvec is a vector of normar / norma for all iterations.
If -ksp_lsqr_exact_mat_norm is set or KSPLSQRSetExactMatNorm(ksp, PETSC_TRUE) called, then anorm is exact Frobenius norm.